SOME RELATIONS OF ORGANIC 
MATTER IN SOILS 






A THESIS 

PRESENTED TO THE FACULTY OF THE GRADUATE SCHOOL 
OF CORNELL UNIVERSITY FOR THE DEGREE OF 

DOCTOR OF PHILOSOPHY 



BY 

FRED ALBERT CARLSON 

FEBRUARY, 1922 



Reprinted from Memoir 6i, September 1922, Cornell University Agriculture 
Experiment Station. 



SOME RELATIONS OF ORGANIC 
MATTER IN SOILS 



A THESIS 

PRESENTED TO THE FACULTY OF THE GRADUATE SCHOOL 
OF CORNELL UNIVERSITY FOR THE DEGREE OF 

DOCTOR OF PHILOSOPHY 



BY 

FRED ALBERT CARLSON 

FEBRUARY, 1922 



Reprinted from Memoir 6i, September 1922, Cornell University Agriculture 
Experiment Station. 



SOME RELATIONS OF ORGANIC MATTER IN SOILS 

F. A. Carlson 

The effect of lime on the organic matter in soils has been 
for some time one of the leading problems for investigation. The 
results that have been recorded, however, are not consistent. 
Some investigators have reported that there is a greater accu- 
mulation of organic matter in limed than in unlimed soil, while 
others have stated the contrary. This difference of opinion is 
not surprising when the methods of experimentation, the soil 
variations, and the climatic conditions are considered. There 
has been, however, too great a tendency to draw conclusions 
from unreliable data. In many cases, attempts have been made 
to study the effect of lime on the organic matter in soils without 
a knowledge of the composition of the soils before treatment. 

In view of the many discrepancies in the reported results. 
the present experiment was designed to ascertain the effect of 
lime on the organic matter in soils under various treatments and 
cropping systems. 

HISTORICAL 

Wheeler and others (1899)' reported that lime decreased 
the percentage of humus in soils under continuous culture of 
cereals. They found also that there was an increase of roots 
and residual organic matter in limed grass plats as compared to 
those not limed. 

Hess (1901) studied the effect of lime on some of the Penn- 
sylvania soils. He stated that liming resulted in a diminution of 
the nitrogen. 

Kossovich and Tretjakov (19u2) stated that the addition of 
calcium carbonate to soil retarded the decomposition of organic 
matter. 

Hartwell and Kellogg (1906) pointed out that the amount of 
humus in limed plats was less than that in unlimed plats. They 
stated also that the effect produced by lime upon the organic 
matter of a given soil was dependable to a considerable extent 
on the degree of acidity or of alkalinity of the soil. 

'Dates in parenthesis refer to References Cited, page. 25. 

3 



4 F. A. Carlson 

Pot experiments by Clausen (1906) conducted with clover 
and oats on sandy soil indicated that applications of lime re- 
sulted in a marked nitrogen hunger, especially during dry, hot 
weather and with non-leguminous crops. 

Van Suchtelen (1910) found in laboratory experiments that 
soils treated with calcium oxide produced less carbon dioxide 
than did unlimed soils. 

Alway and Trumbull (1910) say: 

In a comparison of 22 roialiou plots no distinct relation has been found 
between the composition of the soil and the nature of the rotation. In a 
long cultivated field the till was found poorer in humus, nitrogen and organic 
carbon than the lacustral clay. The amounts of the above three constituents 
found in any of the plots depend more upon the relative proportions of the 
two types of soil occurring on the plots than upon the previous treatment. 

The longer the fields have been kept in grasses mown for hay, the less 
has been the change in composition of the soil. Continuous bare cultivation 
along tree rows has caused greater losses than the alternation of fallow 
and crop in the adjacent fields. The extreme loss of nitrogen, humus and 
organic carbon in 25 years is about one-third of the amounts originally 
present in the prairie. 

Bradley (1912) conducted pot experiments from which he 
pointed out that the nitrogen loss was appreciably reduced by 
legumes. 

Mooers, Hampton, and Hunter (1912) reported that the loss 
of nitrogen was appreciably greater on limed plats than on 
unlimed plats, and that the effect extended below the depth of 
plowing. These investigators stated also that tjiere was an 
increase in percentage of humus on the unlimed sections. 
Mclntire (1913) writes: 
Burnt lime decreased the organic matter when applied alone and lessened 
the accumulation when applied with manure. 

Calcium sulphate and ground limestone increased organic matter. 
Each form of lime resulted in an increase of nitrogen content, gypsum, 
limestone, and burnt lime, being effective in the order named. 

Lipman and Blair (1913) reported that in their experiments 
the limed plats had lost nitrogen to a greater extent than had 
the unlimed plats. 

Gardner (1914) says: "Burnt lime appears to exhaust the 
humus in the soil more rapidly than ground limestone. Burnt 
lime with manure gave returns over manure alone. ... It 
is desirable that the use of lime or limestone lead to larger 
supplies of organic matter in the soil." 

Swanson (1915) reported results based on the chemical anal- 
yses of cultivated and tmcultivated soils in seven representa- 
tive cotinties in Kansas. He pointed out that the elements 



Some Relations op Organic Matter in Soils 5 

carbon and nitrogen have disappeared from the cultivated soils 
to a larger extent than from the uncultivated soils. He showed 
that the cultivated soils had lost, in round numbers, from one- 
fifth to two-fifths of the nitrogen and from one-fourth to one- 
half of the organic matter. 

Potter and Snyder (1916) stated that in a general way the 
total nitrogen determinations in their experiments showed that 
there was a smaller loss or a greater gain of nitrogen for the 
limed soils than for the corresponding unlimed soils. 

Bear (1916) indicated that quicklime reduced the amount 
of carbon and of nitrogen in the soil. 

Potter and Snyder, in a later experiment (1917), concluded 
that lime in the form of a carbonate, under the conditions of 
the experiment, appreciably enhanced the rate of decomposition 
of both original soil organic matter and the organic matter 
of stable manures, oats, and clover when added to the soil. They 
stated that two of the more important results of this were the 
increased availability of plant food and the more rapid depletion 
of the soil organic matter. They pointed out that the latter 
effect would be partially and perhaps entirely offset by the fact 
that with lime larger crops could be grown, which would add 
more organic matter as crop residue to the soil. 

Breazeale (1917) found that calcium carbonate had a slight 
destructive action upon the organic matter of the soil. 

Jensen (1918) stated that in most cases when lime was 
added to alfalfa in basins, greater increase in the humus content 
occurred than when alfalfa alone was used. 

Christie and Martin (1918) state that it is evident from data 
considered that all soils do not react chemically with lime in 
the same manner. 

Bizzell and Lyon (1918) write: "On Volusia silt loam ad- 
dition of quicklime increased the amount of carbon dioxide in 
the soil air. This effect was noticed both on the cropped and 
uncropped tanks. On Dunkirk clay loam quicklime apparently 
produced no effect." 

Swanson and Latshaw (1919) say: 

In the sub-humid section the fields cropped to grain lost one-fourth of 
the nitrogen as compared with the surface soil of the native sod. The al- 
falfa fields contain 5 per cent less nitrogen than the native sod, but 20 
per cent more than the fields in grain 

In the semi-arid section the cropped soil has lost one-fifth of the nitrogen 
as compared with the native sod. Alfalfa fields contained 15.7 per cent 



T) F. A. Carlson 

more nitrogen than the ^^oils in native sod, and 30 per cent more than the 

soils continuously cropped 

In the humid section, the cropped soils have lost 36 per cent of the 
organic carbon present in the virgin sod and those in alfalfa over 21 per cent. 

Lipman and Blair (1920 a I summarized a series of experi- 
ments as follows: 

Lime in the carbonate form was used on a loam soil at the rate of 1 
ton per acre for the first 5 years and 2 tons for the second 5 years in a 
5-year rotation of corn, oats, wheat and 2 years of timothy. No legume crops 
were introduced. Twenty plots with different nitrogen treatment were thus 
limed and twenty similar plots with parallel nitrogen treatment were left 
without lime. 

The total yields of dry matter and of nitrogen for the 10-year period 
were essentially the same for the two sections. 

Analyses of the soil made soon after the work was started and again 
at the end of each 5-year period showed that there was a loss of nitrogen 
from both the limed and unlimed sections. However, the loss from the 
limed section was distinctly greater than from the unlimed section. 

Thus at the end of the 10-year period, there was a positive loss rather 
than gain from the use of lime. 

From this work it would appear that the practice of using lime on 
light to medium heavy soils, when leguminous crops are not grown in the 
rotation, may be questionable. Under such conditions it is quite possible 
that a slightly acid reaction may be desirable to prevent the too rapid 
•oxidation of organic matter. 

The second five-years period showed a distinct loss in carbon 
from both series, but a greater loss from the limed than from 
Ihe unlimed plats. 

Lipman and Blair (1920 b) reported also a series of experi- 
ments which included rotations with legumes. They pointed 
out that during the ten years, the limed plots, with only slight 
exceptions, yielded distinctly larger crops and more total nitro- 
gen than did the unlimed plots. In analyzing the soil they found 
that in a number of cases The limed plots contained more 
nitrogen than did the unlimed plots. 

The same investigators (Lipman and Blair, 1921) reported 
the results of experiments in studying the losses of nitrogen 
and organic carbon from a loam soil (in cylinders with natural 
drainage) which for twenty years had been under a five-years 
rotation of corn, oats (two years), wheat, and timothy. They 
found that in most cases there was a general decline in the nitro- 
gen and the organic carbon content. They pointed out that there 
was a lower nitrogen and organic carbon content in the limed 
soils than in the unlimed soils. They stated also that the legume 
green-manure crops tended to raise the nitrogen content. 

It is quite impossible to make any direct comparison of 



Some Kklatioxs of Organic Matter in Soils 7 

the literature cited, clue to the variations in experimental methods 
and in representation of results. In fact, in many cases there 
are no data to substantiate the statements made. Furthermore, 
the making of comparisons of one plot with another on the 
assumption that the natural variation in fertility is gradual and 
uniform, is subject to severe criticism. It is likewise impossible 
to study the effect of lime on organic matter in soils without 
knowing the original composition of the soils. Also, conclusions 
drawn from computations leased on analyses of soils taken ad- 
jacent to plats under treatment and assuming that the results 
obtained represent the original analyses of the treated plats, are 
questionable. However, the general conception expressed by 
the literature is that plats which have been limed contain less 
organic carbon and less nitrogen than do those which have not 
been limed. There are some exceptions. This conclusion is 
based on very limited experimental data. 

EXPERIMENTAL 

In the present investigation two series of field plats, each 
1-100 acre in size, were used. The plats were sampled both be- 
fore and after treatment. The soil was analyzed for inorganic 
carbon, organic carbon, and nitrogen. 

The soil on these plats consists of glacial material reworked 
by streams and redeposited from glacial lakes (Lyon and Bizzell, 
1918). Owing to its sedimentary origin it is comparatively 
free from stones. The soil has been classified by the United 
States Soil Survey as Dunkirk clay loam. It is a heavy, compact 
soil, and requires careful management. Its average mechanical 
analysis is as follows: 

First Second 

foot foot 

I per cent ) (per cent) 

Fine gravel 0.40 0.13 

Coarse sand 0.63 0.37 

Medium sand 0.83 0..52 

Fine sand 1.85 1.C5 

Verv fine sand 12.90 11.27 

Silt 60.83 53.9.5 

Clay 22.63 32.72 



S F. A. (\\RLSON 

The following chemical composition was determined by 
Lyon and Bizzell from representative samples: 

First Secoocl 

Constituents determined foot foot 

(per cent) (per cent) 

Nitrogen (N) 0.134 0.062 

Organic carbon (C) 1.190 0.300 

Calcium oxide (CaO) 0.340 0.280 

Magnesium oxide (MgO I 0.350 0.450 

Potassium oxide ( K.,0 ) 1.830 2.360 

Sodium oxide (Na,6) 0.860 0.860 

Phosphoric anhydride (P.O.* 0.084 0.079 

Sulfur trioxide (SO,) 0.084 0.053 

Carbon dioxide (CO,) 0.030 0.020 

Lime requirement* (CaO) in parts per million 1,222 1,285 

Lime requirement (CaO) in pounds per acre footf ..4,454 4.918 

* The Veitch method was used for the determination of lime requirement, 
t Calculated from weight of soil as 3,645,000 pounds of dry soil per acre foot 
in the first foot of soil, and 3.827.500 pound? in the second foot. 



.SOIL .SAMrLIXC 

The plats in Series I were sampled both before and after 
the ten-years period. Soil samples were taken from each plat 
to a depth of four feet, each foot being kept separate. Six 
borings were made on each plat. The borings for the same foot 
were carefully mixed together and a 2-quart sample of each foot 
of each plat was retained. The soil samples were air-dried and 
placed in tightly sealed jars. 

The plats in Series II were sampled before and after the 
eight-years period according to the following method: Each 
plat was divided into three parts — N (north), M (middle), and 
S (south). Each one of these sections was sampled as outlined 
for the plats in Series I. 

Pre [Kt ration of the sample 

The air-dried soil was brought to a uniform condition by 
breaking up the soil lumps and carefully mixing. A composite 
sample was taken and was placed in a 1-millimeter sieve. All 
particles of the soil that did not pass through the 1-millimeter 
perforations were discarded. A composite sample was taken 



Some Relations of Orc4ANIC Matter in 8<>ils 9 

from the 1-millimeter sample and was passed througli a sieve 
having 100 meshes to an inch. In this case it was necessary to 
grind the soil in order to pass all of it through the perforations. 

In the determinations of carbon the 100-mesh sample was 
used, while the determinations of nitrogen were made from the 
1-millimeter sample. The use of the finer soil in the determina- 
tion of carbon was based on the uncertainty of obtaining 
complete combustion with the coarser soil. 

The determinations were made in duplicate. All duplicates 
having a wider discrepancy than 0.02 per cent of carbon and 0.01 
per cent of nitrogen were discarded. 

Total organic carbon 

The total organic carbon was determined by the Parr Com- 
bustion Method, as described in Bulletin 107 (revised) of the 
United States Bureau of Chemistry, page 234. 

Total nitrof/en 

The total nitrogen was determined by the Kjeldahl method. 
Ten grams of 1-millimeter soil was digested with 30 cubic centi- 
meters of sulfuric acid (specific gravity 1.84) and 0.4 gram of 
cupric sulfate, in • 500-cubic-centimeter Kjeldahl Pyrex flasks 
at low heat for twenty minutes. Ten grams of potassium sul- 
fate was added and the digestion was continued for three hours. 
The residue was diluted to 350 cubic centimeters of water and 
transferred to an 800-cubic-centimeter Kjeldahl flask; from 80 
to 90 cubic centimeters of alkali solution was added and the 
ammonia was distilled into 1-10 X sulfuric acid. The distillate, 
measuring about 200 cubic centimeters, was titrated with 1-10 
N sodium hydroxide, two or three drops of methyl red solution 
being used as an indicator. 

SERIES I 

Soil treatment and cropping systems 

The plats in Series I were under experimenta,tion for a 
period of ten years, from 1910 to 1919. A statement of the soil 



10 



F. A. Carlson 



treatment of each plat, and of the cropping systems, is given in 
table 1: 

TABLE I. Soil Treatment and Cropping Systems 



Plat 


Soil treatment 


Cropping system 


Fertilizer 


Lime 


7002 


Farm 


manure 


None 


Rotation without legume 


7008 


Farm 


manure 


Burnt lime 


Rotation -without legume 


7003 


Farm 


manure 


None 


No vegetation 


7009 


Farm 


manure 


Burnt lime 


No vegetation 


7005 


Farm 


manure 


None 


Rotation with legume 


7011 


Farm 


manure 


Burnt lime 


Rotation with legume 


7006 


Farm 


manure 


None 


Oats, grass nine years 


7012 


Farm 


manure 


Burnt lime 


Oats, grass nine years 


7014 


Farm 


manure and K2SO4 


None 


Rotation without legume 


7015 


Farm 


manure and K2SO4 


Burnt lime 


Rotation without legume 



The applications of farm manure were made in 1910, 1914, 
and 1918. The three applications were each at the rate of 10 
tons per acre, and were given to the plats that were never planted 
as well as to the cropped plats. The applications of potassium 
sulfate were made annually to plats 7014 and 7015 at the rate 
of 200 pounds per acre. In 1910 and 1915 burnt lime was ap- 
plied to plats 7008, 7009, 7011. 7012, and 7015. at the rate of 
3000 pounds per acre. 

The rotation without legume consisted of corn. oats, wheat, 
and grass two years. In the rotation with legume, clover was 
grown with grass for two years in the first half of the ten-years 
period, and during the second half of the ten-years period a 
legtmie was grown each year as follows: in 1915. soybeans with 
corn; in 1916, peas with oats; in 1917, vetch with wheat; in 
1918 and 1919, clover with grass. 

Plats 7003 and 7009 were never planted to any crop, and 
all vegetation was prevented from growing on them by hoeing. 



Some Relations of Organic Matter in Soils 11 

When corn was growing on the plats in rotation, the implanted 
plats were hoed at the same time and in the same way as were 
the plats planted to corn; when other crops were growing on 
the planted plats, the implanted plats were merely scraped with 
a hoe. 

The mixtures of grasses used consisted of timothy, Kentucky 
blue grass, and redtop. 

Jx'cSllltS 

Orgaiiiv carbon <iiid total nitrogen in plats before and after treat- 
ment 

The results recorded in tables 2 and 3 represent the aver- 
ages of duplicate determinations. The percentages of carbon and 
nitrogen before and after treatment are given, as well as the 
differences and the percentage of increase or decrease for the ten- 
years period. The total amounts of carbon and nitrogen added 
to the plats in manure, have been subtracted from the amounts 
of carbon and nitrogen determined on analysis after treatment. 

The data show that in the first foot, in every case but one, 
the limed plats contained more organic carbon than did the 
unlimed plats. This is very significant in the plats kept in 
grass. Plat 7012, kept in grass and limed, shows an increase of 
20.5 per cent of organic carbon in comparison to an increase of 
14.5 per cent in plat 7006, which had the same treatment and 
cropping except that it was not limed. Plat 7002, cropped in 
rotation but not limed, shows a decrease of 24.5 per cent of or- 
ganic carbon in comparison to a loss of 3.1 per cent in plat 7008, 
which had received lime. This difference is not attributed en- 
tirely to the lime. Plat 7002 was exposed to greater erosion and 
more complete drainage than was plat 7008. All plats in rota- 
tion show a decrease in organic carbon in the first foot, while 
there is a marked gain in organic carbon in the first foot in 
the plats kept permanently in grass. 

The use of legumes in rotation did not materially affect the 
organic carbon content. 

Plat 7009. which was kept bare, lost a marked percentage 
of organic carbon in the first foot. 

The percentages of organic carbon in the second foot are 



12 



F. A. Carlson 



.s « 


c c 




c-i t>l 


d 


cc 







q 

C5 


'•jr 


t-; 


r-i 


=»H '- 


w o 


T^ 


■^ r- 




1—1 










^^^ 




^% 


Q, ■*- 


! 


i 


1 




+ 




+ 




+ 


1 
















































0) ^ 




Lt 





ri 




CC 




L!C 


LC 


q 


00 




ll 


•^ 


^•■ 


X 




d 




■*' 


d 


d 


d 


U V. 


■M 




c^ 








^H 


CO 








II. '-^ 




1 


1 




1 




+ 


+ 




1 




























TT 


o: 


N 


10 


irt 


00 




\a 


00 


00 


01 




O-w 


c- 


cq c^ 


Tf< 


U5 


<M 




■* 


CO 










O O 


o 


r-j 


q 


q 


q 







q 


tH 







O O 
CC 


c 





d 


d 


d 




d 


d 


d 


d 


F 


I 


1 1 


1 


1 


+ 




+ 


1 


+ 


1 


a; 




Tf 


■^ 


c~ 




CO 




c- 


LO 





?o 


II 


o 


■* 






C5 




00 





■^ 


05 


C 


CC 

o 


q 



■^ 




q 
d 




1— I 
d 


CO 

d 


1— 1 
d 


q 
d 








f 




1 




+ 


+ 


i 


1 




o o 
o o 


c~ 


'^ 00 


LC 


LC 


00 




\A 


c^ 


LC 


00 




IC 


C<1 -^ 


eg 


1^ 


<M 




■^ 


CC' 





(cg 


._ 


■* 


Tf CO 


■* 


CO 


"*. 




U5 


LC 


«r 


\a 


l=! 


Hi •■« 


,— ■ 


— ' 


— ' 


— ' 


d 




d 


d 


d 


d 


t< 03 


K 






















^ S 
























4-J *-H 


























+J ^ 


tx 


\r-. \r- 


:^ 





t^ 




CO 


c^ 


M 


OS 


l§ 


CC 


t- I>1 


^ 


■^ 


t^ 




t- 


Oi 


Cvl 





3-. 


CC q 






CC 




'^. 


t~ 


CC 


CO 




Is. '-^ 


~ 




^^ 




1-H 




i-i 


" 




T-i 




-c 


•»c 


LC C: 
















10 


c- 


c- 




o o 
o o 


CC 


Tf C^ 


D- 


c^ 










t— 


Oi 


co 


_ 


\a 


IC' ■* 


Tf 


'^ 


■* 




irt 


10 


■* 


LO 


tl 


CD «-■ 


d 


d d 


==^' 


- 


d 




d 


d 


d 


d 


=25 














































H) ni 
























pq 1 


+J ^ 


cj 


J: 


c- 









t^ 


c^ 


C-l 


m 


.^8 


■* 




c^ 




t- 




00 


00 


ID 





w 


•rr 


•* 




■<* 




^ 


■* 


■^ 


■«t< 




fc=M 


^^ 


^ 






T-I 




l-i 




i-i 


iH 
























0) 
























a 
























;=; 






















., 


- 


c 


3 


C 


S 03 


•2 a 

cS — ' 





S 3 


a> 




(D 


flee 


^0 




3 
■J 


O 


■2S :a 


5 

*3 bC 


.2 3 


S 




a 


•Bt^' 


?, 

5^ 




6 


cS 


cS 0) 


oj Ol 


'"' 




•— ^ 


cd 


rt 


c 


D 


4-j 

Q) 


-*-> - CD 
Q^ hfi <i> 


lioT 


*J r-l 

a> 





of 


tP 


0" 


0) 


aT 


r 






s^ ^g s-^ 

g-fl ^S >fl 
o§ ^§ :z;§ 


S 


















(ra 


ex CO 


Oi 


10 


i-i 




^ 


C<1 


•«*l 


Ui 


c 


c 














1-1 







T-l 


tH 


T— * 


































5 


■ 





t^ l> 


c- 


t- 


t- 




t^ 


c- 


1^* 


t^ 



Some Relations of Organic Matter in Soils 



13 



z 






a 






+ 



+ 



+ + 



4- 



o o 

O o 

a,. --4- 

7} 



+ 



+ + 



+ + 



, 
















r^ +J 


CO 


■^ 


c- 


o o 




lO 


lit 


cj o 




o 


o 


Oi -•« 


o 


o 


o 


m 








Ho 


oo 


CO 


as 
o 


•S § 


o 


I— 1 




tq =" 


o 


o 


^ 



o o 



o o 



o — ' 



fin 



pa 



a 



01 rtO j-iCJ 

a §»?. §02 




14 F. A. CA1U.80N 

less consistent than those in the first foot. This inconsistency 
may be accounted for by lack of soil uniformity. 

The limed plats not only contained more organic carbon, 
but also gave higher yields, than the unlimed plats. The yields 
are expressed in graph form in figure 1 (page 17). 

With one exception there was a greater percentage of nitro- 
gen in the limed plats than in the unlimed plats. The plats in 
rotation all showed a loss of nitrogen in the first foot for the 
ten-years period, while the plats in grass increased in nitrogen. 
Plat 7009, which was kept bare, lost a marked percentage of 
nitrogen in the first foot. Plat 7011, on which the rotation in- 
cluded legumes, lost a smaller percentage of nitrogen in the first 
foot than did the plats in rotation without legumes. 

These results are consistent with the results obtained on the 
lysimeter tanks (Lyon and Bizzell, 1918). The soil in the lysim- 
eter tanks was obtained from The plats used in these experi- 
ments. It was found that the nitrogen in the drainage water 
from the lysimeter tanks was less where the tank soils had 
been kept in grass, than in a rotation. It was shown also that 
the tank soils kept bare lost more nitrogen than the cropped 
tank soils. 

}tatio of carbon to nifroffen in plats hffore and after treatment 

The ratios of carbon to nitrogen in plats before and after 
treatment are given in table 4. The data show the close relation 
between these two elements in the soils studied. The ratio was 
wider in the first foot of soil than in the second foot. The variotis 
treatments did not cause any constant change in the carbon- 
nitrogen ratio. The effect, if any. was too inconsistent to be con- 
sidered significant. 

The results compare favorably with those obtained by Hess 
(1901). He found that the ratio of carbon to nitrogen was not 
materially affected by the treatment applied. Dyer (1902) also 
reported that the carbon and nitrogen contents of the upper 
stratum of the soil were higher than those of the lower stratum, 
and that the ratio of carbon to nitrogen was wider in the upper 
stratum. Alway and McDole (1916) likewise found that the ratio 
of carbon to nitrogen was lower in the second foot than in the 
surface foot. 



S(i-ME Rklations of Organic Matter in Soils 



15 





































~ 




























•— 


r-, 


tH 


1—1 


1-H 


1—1 


1—1 


rH 


rH 


rH 


rH 




































X 


ra 


Ci 


(M 


!>; 


rH 


CO 


T-< 


■^ 


C/D 


v: 






^ 


o 


>3 


t^ 


« 


t-^ 


TJ^ 


T}J 


d 


c/i 


t-^ 


Lit 






























































X 


1/ 


























^ 


CO 


























"t;; 




























^ 




























~ 




























i. 




























1 


■4-S 






























i-H 


^ 




tH 


1-1 


1-1 


rH 


rH 


^ 


-H 






< 


Tj- 


c~ 




;.; 


O 


Oi 


t- 


-i' 


•i' 


lO 








■bJ 


^^ 


T-H 




o^ 


ai 


ai 


d 


rH 


i^ 


d 




"^ 




CO 


^ 


tH 












^ 


rH 


T-i 




'"-■ 




^ 
















































































<x> 




























■aC 




























p 














































































































C 
























































" 




— 




















































■p 




'■"■ 


■— 


^^ 


1-1 


-^ 


I— 1 


rH 


rH 


^ 


1— < 


7-t 




5 




■r 


i;' 


-* 


LC 


t~ 


<Xi 


OO 


O 


^' 


'•^ 


^V 




o 


33 

0) 


a: 




cc 


lO 




CO 


LO 


t-^ 


-yj 


l-^ 








■" 




























r 


































































1—1 














































^ 


•— 


T— 


,-1 




Oi 




rH 


C/5 


rf- 


•J 


n 








v: 




T-H 




d 

rH 




d 

rH 


d 


d 


d 




















'$ 


43 








^ 






1 




£ -^ 


~ 2 
•2.3 

P 0- 


3 


•2 a 

bo ^ 


otation 

mes 

e 


■otation 
mes 
e, lime 


_X' 


6 


_ o 

c P 


O a; 






e 






2 S 


O 03 




Crop r 

legu 

Manur 


l-l 3 tH 


^ 3 


2 S 


p X 


a 2 

P X 










5^ 


o g Z g J^ S 


Q S Og 


OS 


CS 


c S 










S<1 


oo 


CO 


03 


ift 


i-{ 


to 


ira 


rj" 


lO 






— 




o 


o 


o 


o> 


o 


rH 


o 


rH 


r^ 


^^ 






^— 




o 




o 


o 


o 


O 


o 


O 


o 


o 










c~ 


?• 


t- 


t- 


t- 


t- 


c^ 


t^ 


L^ 


c- 



16 



F. A. Oaulson 



Removal of iiifrorjeii from the soil in crops grown on the plats in 
iSeries I 

The amounts of nitrogen removed in the crops were esti- 
mated and are recorded in table 5. The nitrogen is expressed 
in pounds per acre for the ten-years period. 

TABLE 5. Amount of Nitrogen in Crops. Series I 



Plat 


Crop 


Fertilizer 


Burnt 

lime 

(pounds) 


Nitrogen in crops 
(pounds per acre, 
total for ten years) 


7002 


Rotation with- 
out legume 


Farm manure 





684 


7008 


Rotation with- 
out legume 


Farm manure 


9,000 


798 


7005 


Rotation with 
legume 


Farm manure 





817 


7011 


Rotation with 
legume 


Farm manure 


9,000 


948 


7006 


Grass 


Farm manure 





325 


7012 


Grass 


Farm manure 


9.000 


.354 


7014 


Rotation with- 
out legume 


Farm manure and K2SO4 





844 


7015 


Rotation with- 
out legume 


Farm manure and K2SO4 


9,000 


868 



It appears that the nitrogen varies with different crops. 
The greatest removal of nitrogen was in the crops in rotation 
with legumes. The hay crops removed less than half the 
amounts of nitrogen estimated in the crops in rotation with 
legumes. These results are of extreme importance in consider- 
ing the total nitrogen in the soils of these plats recorded in 
table 3, in which, as already stated, it is shown that the plats 
kept in grass increased in nitrogen in the first foot, while the 
plats in rotation with legumes and those in rotation without 
legumes decreased in nitrogen. The fact that less nitrogen was 
removed from the grass plats may aid in some degree in explain- 
ing these differences in percentages of nitrogen. 



Some Relations of Organic Matter in Soils 



17 



Total yields of crops on plats in Series I 

The total yields of crops in Series I are represented in 
figure 1. 



Field 

weight 
(lbs.) 



40" 



300 



200 



14r/TMOl/T L/Af£: 
WITH l.7M^ 



I 



I 



Plat 



I 



i 



1 



I 



i 



7002 7008 


7005 7011 


7006 7012 


7014 7015 


Crop rotation 


Crop rotation 


Grass 


Crop rotation 


without 


with 




without 


legume 


legume 




legume, 
+ K,SO, 



FlO. I. TOTAL PLAT YIELDS FOR TEN-YEARS PERIODS^ SERIES I 

In every case there was an increase in crop yield on the 
limed plats over that on the unlimed plats. It seems logical to 



18 F. A. Carlson 

assume that an increase in yield is associated with an increase 
in roots and residual organic matter, which may explain why the 
organic carbon and the nitrogen were generally higher in the 
limed plats than in the unlimed plats. 

The total yields were less on the plats kept permanently in 
grass than on the plats in rotation with legumes or on those in 
rotation without legumes. It has already been pointed out. in 
tables 2 and 3, that the plats in rotation lost more organic car- 
bon and nitrogen in the first foot than did the grass plats. 

SERIES II 

In order to obtain further information on the effect of 
treatment and cropping on the organic carbon and the nitrogen 
in soils, the plats in Series II, located adjacent to plats in Series 
I, were analyzed. These plats, as already stated, received ap- 
proximately the same treatment as the plats in Series I, the only 
marked differences being that the plats of Series II were started 
one year later than the plats of Series I, and that they received 
only two applications of manure. 

Only the first foot was analyzed, due to the failure of the 
second foot in Series I to show any consistent results of experi- 
mental value. 

The results obtained are recorded in tables 6, 7, and 8. 
These tables are not discussed separately, due to their close 
correlation with the results of Series I. 

The points emphasized in discussing the results of Series 
I may well be applied to Series II. However, the results in 
Series II are much more striking. The limed plats, as was 
found in Series I, show in general a higher percentage of organic 
carbon and of nitrogen than do the unlimed plats. The limed 
plats also gave higher yields than did the unlimed plats. There 
was a decrease in organic carbon and in nitrogen in the plats 
cropped under the rotation without legumes, with one exception. 

The most interesting phase of these results is that the plats 
In rotation with legumes showed an increase in nitrogen. The 
percentages are very significant. Plats 7205 and 7211. in rota- 
tion with legumes, increased 4.2 and 6.7 per cent, respectively, 
in comparison to plats 7202 and 7208, in rotation without leg- 
umes, which decreased in nitrogen 12.2 and 7.1 per cent, re- 
spectively. 



Some Relations of (Organic Matter in Soils 



19 



u 
























° = ^ 






















^ to 

— OJ 53 




00 


"^ 


lO 


C5 tH 


CO (M 


t~l 


^^ 


t-; 




?^ ^ S 




1-! 


CO 


CO 


t-^ s<i 


T-i d 


ai 


d 


T-i 






T-H 




M 




M 1-H 


tH 


tH 






^ V --^ 

■_ •" V 




1 


+ 


1 


1 i 


1 + 


+ 


1 


1 
















































i-' 






















c 




t- 


c> 


C>1 


T-J ^-1 


C^3 T-H 


o 


-f 


CD 




s 




tH 


CO 


oo 


^ <M 


"* CD 


o 


o 


T-I 






o 


o 


tH 


o o 


CO i-H 


<M 


T-I 


o 




I 




o 


d 


d 


d d 


d d 


d 


d 


d 




- 






+ 


' 




1 + 


+ 


' 


' 








6C 


CO 


o 






tH ?o 


■*! 


CO 










c3 


OS 


o 


Oi 


r-l 'CO 


lO LO 


tH 


<M 


1* 




-I-J 




c-^ 


Ol 


lO 


t- Ci 


l~ 1— 1 


C-1 


05 


Oi 




^ 


o 
p 


> 

< 


d 


d 


d 


d d 


d r-i 


T-1 


d 


d 
















































7i 
























li 


■^ 






















^ 


^ 
























r" 


M 




















X 


fJ^ 


o 


Oi tC CO 


T-( T-H O 


«D CO C<I 


T-t 03 <M LO LO CO 


C^l CC 'CD O C-5 CO 


l:~ OO 00 


t- o o 


C^J o o 








t- OS r-l 


cq C<1 t- 


Oi iO Oi 


cri i-H «5 o c CO 


CC C^l CD 1— 1 O lO. 


oo <M CV1 


00 CD c^^ 


CO CO o 




< 






00 C~ C-; 


05 CS CO 


ID LO lO 


GO t-- iq o O OS 


th o o r:<\ T-; i-< 


CO (M O O «5 c- 


O GO Oi 




odd 


d d d 


d d d 


d d d 1-H 1-i d 


^H ,-i o 1—1 1-! i-i 


TH T-i T-i 


i-l o o 


T-i d d 








a. 


LO 


to 


CO 


M ■* 


CO lO 


■* 


i> 


t> 




•t^ 




a 


o 


t^ 


t^ 


I- o 


(35 Oi 


T-I 


(M 


lO 




A 




C5 


oo 


t>; 


t- o 


O Oi 


o 


O 


as 




l! 




S 


d 


d 


d 


d T-i 


rA d 


T-i 


r-i 


d 




J^ 


■*^ 


t» 






















o 


<; 




















a3 




^ 


^ 


^^ ^ 


., ^ .' 




_/. 


■* <3i CO 




CO .— 1 T— 1 


LCt' LC GO 


L;:><3ii^i--o0i-i-«fc<ico 


O CO CD CD CO C<I 


00 O •* CO CD T-I 








G 


C-l OS o 


OOOC01-D6oC-C35COCO«SCO=X> 


C- t- CO C<1 •* tH 


CO CO c- 


t- Oi rH 


OO c- o 




CD 


•^ 


o 


Oi 00 C5 


as CO CO 


C- t~ t-; 


c- t- c- o a> 05 


iHr-HCTiOOiOOOCO 


T-I Ol Oi O 00 OS 




^ 


^ 


Xi 


d d d 


d <:i 'd' 


s s s 


S S (S rA id 'd 


l-i T-i d tH d T-1 


T-I T-I O 


T-i d d 


^ o o 




^ 




o 




















;r 






ZScn 


Z^Ui 


^gco 


'Z^mZ^Ui 


^gcc^goj 


^^CO 


issw 


;zi^!:n 














A 


,a 






X' 

s 














*^ 


4-> 










__j 










•^ 


•^ 






> 




S 




o 






Ig § 


3 g 


a> 




§03, 




0, 




4-> 

o cp 

'i-i u 

p ° 


O <D 




z^ 6 ^ 


'+2 S 

o g oT a; 

^ r-( ;-( !h 


P 

to 3 


^ tii' 

-l-J . 
O (D 
f-< J-i 

P § 

5^ 


2 M 

+-> . 
O 0) 










oo 


r.-^ 


OS LO 


^ CD 


IM 


•^ 


lO 




-~ 




o 


d 


o o 


T-I O 


T— 1 


tH 


T— 1 






- 






c^ 




CM CM 








c- 





20 



F. A. Carlson 



°°a; 














C Q) oj 


CO 


T-; 


c-^ 


O M 


t-; O O O 


OS 


0) £0 cp 


M 


l> 


d 


Irt M^ 


d oo lo d 


d 


O CS ^H 


i-H 




rH 


tH 






03 O 

u ^ ^ 


1 


1 




1 + 


+ + + 1 


i 


S "xi 














I1..9 


_ 














(D 
















O 

13 




■>* 


00 


00 


« LO 


00 OS ^ t- 


, 




1—1 


o 


1—1 


iH O 


o o o — 


— 


CP 




o 


o 


o 


O O 


o o o -. 


^ 


03 




o 


o 


d 


d d 


o d d o 


— ■ 


^ 




1 


1 


1 


1 + 


+ + + 




5 




















03 


















M 


T— 1 


•*! 


o 


1-1 CO 


00 CO Lft OS 


t— 


+J 




173 


o 


o 


o; 


05 Cq 


M M (M o 


o 


*-H 




;h 


T-; 


T— 1 


o 


O r-H 


l-j I-i ^H tH 




a 


o 
o 


03 

> 

< 


o 


d 


d 


d d 


S c6 d> d 


=■ 


cS 


*H 
















CP 


















EC 














0) 


E 


CO lO 05 05 OS •* 


O C.'J t- 


05 ?0 05 •<*< OS CO 


■*-.i<c-(Mt-ooo'*cqosioco 


Ut 1-1 Lft 




_o 


Oi O 05 O O OS 


05ai00a5a5t-C<li-IC<lC000i-IC<JC^T-l'^C<lrHiHOO 


rH O O 


«1 




o 

CD 


O i-J o 


rH r-l O 


O C=; O 


O O O i-H rH i-t 




rH rH 1— 


o o o 


odd 


d d d 


d d d d d d 


dddddddddddd 


d d d 






03 


















M 


lO 


N 


CO 


C- 00 


O CO OS -X 


oc 


CD 




d 


1— 1 


rH 


o 


O iH 


CO T-l tH tH 


© 







1—1 


1-1 


1-; 


r-t 1-1 


iH 1-1 rH rH 




a 

"cS 

9 


o 
o 

•-M 


<1 


o 


d 


d 


d d 


d d S <zi 




o 
ti-i 

CD 




tn 




, 






._ .^ , 




O lO O O C<1 CO 


tZ) iH lO 


iH 1-1 O C<1 00 CO 


«5-*O00-^000SL0NOi-HC- 


Ct 1— 1— 


E 


!:] 


(M T-l i-l 


(M T-l O 


Oi-IOt-ItHOC<I<MO 


COCOrHrHi-IOCOrHrHCOCOC 


i4 rH O 




_0 


1-J 1-1 iH 


i-l iH 1-1 


tH T-l 1-1 








OOOOOOOOOOOOOCSO^OOOOOOOOOOC 


d d d 


W 




o 


















03 

m 


^sm 


:2;g(w 


^§cc 


;z;ga!:z;gM 


Z§a2;z;§M^Scn2gMi 


ZSc/: 


' 


'^ 


■' 




' ' 


















0/ 












^ 


xi 


£ 












-bj 


■i^ 




-w 










•^ 


•^ 




s 




a 


C3 03 


a 


S <^ fl 


fl 03 (p ctO 


- c 


CD 




+-> 

03 

O 03 


.2 a 

O O) 


o =5 


.2 a .2 

+j « 03 

So ? S S ?> 
O 03 £ -=- C3 


§ a B °^i 

O a 03" 0) 03" P Q)* 


3* C' 


H 




2| 


2| 


P.Sg gg |g as 
o.^§ Sl 2| 2| 


2| 






oS 


qS 


zs 


Zg o § 


o S O^ Og Qg 


5s 


-tJ 




«<l 


00 


03 


OS irt 


rH CD CO -* 


Lft 


nS 




o 


o 


O 


o o 


rH O rH i-< 


r- 


T^ 




cq 


c^ 


cq 


<M C^l 


CO <?<l CO CO 


*q 




-M 




r— 


r- 


r~- 


t^ r^ 


t^ ^- c- r- 


t~ 



Some Relations of Organic Matter in Soils 



21 



TABLE 8. Ratios of Carbon to Nitrogen in Plats before and after 
Treatment, Series II, First Foot of Soil 







Carbon-nitrogen ratios 


Plat 


Treatment 


Before treatment 


After treatment 


7202 
7208 
7203 
7209 
7205 

7211 

7206 
7212 

7214 

721.5 


Crop rotation 

Manure 

Crop rotation 

Manure, lime 

No vegetation 

Manure 

No vegetation 
Manure, lime 
Crop rotation with 

legume 
Manure 
Crop rotation with 

legume 
Manure, lime 
Grass 
Manure 
Grass 

Manure, lime 
Crop rotation 
Manure, K„S04 
Crop rotation 
Manure. K.S04, lime 


7.9:1 
7.8:1 
7.2:1 
7.2:1 
8.5:1 

9.1:1 

8.8:1 
8.2:1 
8.9:1 
8.9:1 


7.9:1 
8.7:1 
6.6:1 
7.9:1 
7.9:1 

8.5:1 

9.5:1 

9.7:1 
8.5:1 
8.8:1 



The plats in grass showed a decided increase in organic 
carbon and in nitrogen. 

The carbon-nitrogen ratios were lower than those in 
Series I. 



Removal of nitrogen from the soil in crops grown on the plats in 
Series IT 

The amounts of nitrogen removed in the crops grown on 
the plats of Series II were estimated and are recorded in table 
9. The nitrogen is expressed in pounds per acre. 

The results compare favorably with those obtained in the 
study of the plats in Series I. In considering the nitrogen in 
the soils of the plats in rotation with legumes, as recorded in 



22 



F. A. Carlson 



TABLE 9. Amount of Nitrogen in Crops. Series II 



Plat 


Crop 


Fertilizer 


Burnt 

lime 

(pounds) 


Nitrogen in crops 
(pounds per acre, 
total for eight years) 


7202 
7208 
7205 
7211 
7206 
7212 
7214 

7215 


Rotation with- 
out legume 

Rotation with- 
out legume 

Rotation with 
legume 

Rotation with 
legume 

Grass 

Grass 

Rotation with- 
out legume 

Rotation with- 
out legume 


Farm manure 

Farm manure 

Farm manure 

Farm manure 

Farm manure 

Farm manure 

Farm manure and K.SO4 

Farm manure and K,SO., 



9.000 


9.000 


9.000 


9,000 


555 
714 
690 
892 
312 
397 
652 
703 



table 7. and that removed by the crops, the advantage from the 
growing of legumes is fully substantiated. The crops in rota- 
tion with legumes removed more nitrogen than did the crops in 
rotation without legumes. In this connection it is important to 
note also in table 7 that the plats in rotation with legumes con- 
tained more nitrogen than did the plats in rotation without leg- 
umes. While the plats kept in grass contained more nitrogen 
than did the plats in rotation, there is a marked difference in 
the amount of nitrogen removed by the hay crop as compared 
with the crops in rotation with legumes. The results show that 
the rotation with legumes used in these experiments supplied 
more nitrogen than did the rotation without legumes or the 
grass. 



Total i/iclds o/' cro/is on plats in >S'cr?r.s // 

The total yields of crops in Series II are represented in 
figure 2. The limed plats show a greater yield than the unlimed 
plats. This was true also of the plats in Series I. The total vields. 



SdME KkLATIONS of ORGANIC MATTER IN SOILS 



23 



however, of both the limed and the unlimed plats in Series II 
are less than those in Series I. It may be pointed out here that 
the plats in Series II contained less organic carbon and nitrogen 
than the plats in Series I. This may indicate that there is some 
relation between organic carbon and nitrogen, and yields of 
crops. 



Field 

Aveight 

Ubs.) 



^ 



kviTHOLrr limb 
/fvr/y I. /MET 



600 




Plat 



7202 T20S 


7205 7211 


7206 7212 


7214 7215 


Crop rotatio'i 


Crop rotation 


Grass 


Crop rotation 


without 


with 




without 


legume 


legume 




legume, 

+ K,SO, 



Fig 2. TOTAL PLAT YIELDS FOR EIGHT-YEARS PERIODS, SERIES II 



24 F. A. Carlson 

The most important result shown in figures 1 and 2, as 
related to the present investigation, is the increase in yields of 
crops on the limed plats over those on the unlimed plats. 

SUMMARY 

A study of the effect of various treatments and cropping 
systems on the organic carbon and the nitrogen in soil is re- 
ported in this paper. The soil is classified as a Dunkirk clay 
loam. The plats were each 1/100 of an acre in size and were 
arranged in two series. The treatments included manure, potas- 
sium sulfate, and lime. The cropping consisted of a rotation 
without legumes, a rotation with legumes, and grass perma- 
nently. The experiment was conducted for periods of eight and 
ten years, respectively. 

The plats were sampled for the first- and second-foot strata 
before and after treatment. 

The organic carbon and the nitrogen were determined. 

The results of the two series compared favorably. 

In general the limed plats in both series contained more 
organic carbon and nitrogen than did the unlimed plats. 

There was a decrease in organic carbon and in nitrogen at 
the end of the period of experimentation on the plats in rotation 
without legumes. 

The plats kept in grass showed an increase in organic car- 
bon and in nitrogen. 

The plats in rotation with legumes contained more nitro- 
gen than did the plats in rotation without legumes. The plats 
in rotation with legumes in Series II showed a marked increase 
in nitrogen. The increase was greater in the limed plats than 
in the unlimed plats. This fact seems to indicate that the leg- 
umes had some influence on the nitrogen content of the soil 
studied. 

The organic carbon and the nitrogen were lower in the 
plats of Series II than in the plats of Series I. 

The limed plats produced higher yields of crops than did 
the unlimed plats. 

The plats in Series I gave higher yields of crops than did 
the plats in Series II. 

The results suggest that there is some relation between or- 
ganic carbon and nitrogen, and yields of crops. 



Some Relations of Organic Matter in Soils 25 

The crops in rotation with legumes removed more nitrogen 
from the soil than did the crops in rotation without legumes. 

The plats kept in grass lost less nitrogen in the crops than 
did the plats in rotation with legumes. 

There is a close relation between the organic carbon and 
the nitrogen. The ratio is wider in the first foot of soil than 
in the second foot. 



REFERENCES CITED 

Alway^ Frederick J., and McDole, Guy R. The loess soils of 
the Nebraska portion of the transition region : I. Hygro- 
scopicity, nitrogen, and oro-anic carbon. Soil sei. 1 :197-238. 
1916. 

Alway^ F. J., AND Trumbull, R. S. A contribution to our knowl- 
edge of the nitrogen problem under dry farming. Jonrn. Indus, 
and eng. chem. 2 :135-138. 1910. 

Bear^ Firman E. Effect of quicklime on organic matter in soils. 

Amer. Soc. Agron. Journ. 8 :111-113. 1916. 
Bizzell^ J. A. AND Lyon. T. L. The effect of certain factors on 

the carbon-dioxide content of soil air. Amer. Soc. Agron. 

Journ. 10:97-112. 1918. 

Bradley, C. E. The soils of Oregon. Oregon Agr. Exp. Sta. 

Bui. 112 :l-48. 1912. 
Breazeale, J. R. Formation of ''black alkali" (sodium carbon- 
ate) in calcareous soils. Journ, agr. res. 10:541-590. 1917. 
Christie, A. W.. and Martin. J. C. The chemical effects of CaO 

and CaCOs on the soil. Part II. The effect on water-soluble 

nutrients in soils. Soil sci. 5 :383-392. 1918. 
Clausen^ H. [German title,] Can calcareous fertilizers be held 

responsible for a deficiencv of nitrogen in soils? Illus. landw. 

Ztg. 26:674-675. (Cited in Exp. sta. rec. 18:622-623. 1907.) 

1906. 
Dyer, Bernard. Results of investigations on the Rothamsted 

soils, U. S. Office Exp. Sta. Bui, 106:1-180. Reference on 

p. 29.) 1902. 

Gardner, Frank D. The use of lime on land. Pennsvlvania 
Agr. Exp. Sta. Bui. 131:167-204. 1914. 



26 F. A. Carlson 

Hartwell, B. L., AM) Kellogg, J. W. Ou the elfect of liming 
iipou certain cou.stitiients of a soil. Rhode Island Aur. Exp. 
Sta. Kept. 1905 : 242-252. 1906. 

Hess, Enos H. Effect of various systems of fertilizing upon the 
humus of the soil. Pennsylvania State Coll. Ann. rept. 1899- 
19002; 183-202. 1901. 

Jensex. Charles A. Humus in mulched basins, relation of 
liumus content to orange production, and effect of mulches on 
orjuige production. Journ. agr. res. 12:505-518. 1918. 

KossoviCH, P.. AND Tretjakov, I. [Russiau title.] On the influ- 
ence of cahium carbonate on the progress of decomposition of 
organic matter. Zhur. Opuitn. Agron. 3 :450-484. ( Cited in 
Exp. sta. rec. 14 :427. 1903.) 1902. 

LiPMAN. J. G.. AND Blair, A. W. Field experiments on the avail- 
abilitv of nitrogenous fertilizers. New Jersey Aur. Exp. Sta. 
Bui. 260:1-33. 1913. 

The lime factor in permanent soil improvement. I. 



Rotations without legumes. Soil sci. 9:83-90. 1920 a. 

Tiic lime factor in i)ernianeiit soil improvement. 



II. Rotations with legumes. Soil sci. 9:91-114. 1920 b. 

Xitrogen losses under intensive cro)>ping. Soil sci. 



12:1-19. 1921 

Lyon, T. LvTTr.ETox. and Bizzell^ James A. Lysimeter experi- 
ments. Cornell Univ. Agr. Exp. Sta. Memoir 12 :1. 115. 1918. 

McIntire, W. H. Results of thirty years of liming. Pennsyl- 
vania State Coll. Ann. rept. 1911-122:64-75. 1913. 

MooERS, C. A., Hampton, H. H., and Hunier, W. K. Fertility 
experiments in a rotation of cowpeas and wheat. Part III. 
The effect of liming and of green manuring on the soil content 
of niti-ogcu ;md liumus. T^'niv. Tennessee Agr. Exp. Sta. Bui. 
96 :25-43. 1912. 

Potter. R. S., and Snyder, R. S. Carbon and nitrogen changes 
in the soil variously treated: soil treated with lime, ammo- 
nium sulfate, and sodium nitrate. Soil sci. 1 :76-94. 1916. 

Decomposition of green and stable manures in soil 

Journ. agr. res. 11 :677-698. 1917. 



Some Relations of Organic Matter in Soils 27 

SucHTELEN^ F. H. H. VAN. Ueber die Messang der Lebenstaetig- 
keit der aerobiotischen Bakterien im Boden durch die KoMen- 
saeureproduktion. Centbl. Bakt. 2:28:45 89. 1910. 

SwANSON^ C. O. The loss of nitrogen and organic matter in eiilti- 
vated Kansas soils and the effect of this loss on the crop-pro- 
dncing power of the soil. Journ. indus. and eng. chem= 7 :529- 
532. 1915. 

SwANSON^ C. O., AND Latshaw^ W. L. Effect of alfalfa on the 
fertility elements of the soil in comparison with grain crops. 
Soil sci. 8 :l-39. 1919. 

Wheeler, H. J., Sargent, C. L., and Hartwell, B. L. The 
amount of humus in soils and the percentage of nitrogen in the 
liumus, as affected by applications of air-slacked lime and cer- 
lain other substances. Rhode Tshnid Ai^v. Exp. Sla. Ann. 
rept. 12:152-159. 1899. 



Memoir ,17. A Study, by thi: Cro/j Survey MeUiod, uf b'actors Inltuencing the I'ield of 
fotatnes, the fourth preceding number In this series of publications, was mailed on September 
27, 1922. 



^ 



LIBRARY OF CONGRESS 



e p>o>9 683 476 4 



